The Yokosuka K4Y/ Navy Type 90 Seaplane Trainer was a Japanese floatplane trainer of the 1930s.
A single engine two-seat biplane, 211 K4Ys were built between 1933 and 1940, serving as the Imperial Japanese Navy’s basic floatplane trainer throughout the Second World War.
Yokosuka built two prototypes, powered by 90 hp (67 kW) Hatakaze four-cylinder air-cooled inline engines in 1930, flying in 1930, and after successful testing, a version powered by a 130 hp Gasuden Jimpu radial engine was ordered into production as the Navy Type 90 Seaplane trainer, with the short designation K4Y1.